Convert XML to XML with XSLT Add namespace problem

I need to convert one XML into another XML document using xslt and add a namespace to an element.

I need to be able to add the xmlns="http://www.opentravel.org/OTA/2003/05" to the POS element to produce the following:

<OTA_HotelDescriptiveInfoRQ xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" EchoToken="Test" PrimaryLangID="en" xmlns="http://www.opentravel.org/OTA/2003/05">
<POS xmlns="http://www.opentravel.org/OTA/2003/05">
<Source>
<RequestorId ID="999" ID_Context="Me" />
</Source>
</POS>

Here is what I thought would work in the xslt document:

                  <xsl:element name="POS" namespace="http://www.opentravel.org/OTA/2003/05">
                        <xsl:element name="Source">
                              <xsl:element name="RequestorId" use-attribute-sets="requestor" />
                        </xsl:element>
                  </xsl:element>

However the resulting xml document comes out without the namespace as:

      <POS>
            <Source>
                  <RequestorId ID="999" ID_Context="Me"/>
            </Source>
      </POS>

I also need to insert the same namespace in another element further down the document, but obviously that fails too.

Any help would be really appreciated.